1. Field Of The Invention
The field of this invention pertains to fifth wheel stands, or hitches as used on railway flat cars for securing semi-trailers and more especially relates to repair procedures for the top plate of such hitches.
2. Description Of The Prior Art
With the advent of piggy back operations in the railroad field the use of fifth wheel stands on railway cars has become quite common and hitches of this type are extensively used in connection with the transportation of trailers on railway flat cars. However, railroad operations are quite severe for cars in such service, what with hump yard switching and the like, as well as general over-the-road service.
Such service imposes draft and buffing shocks on the cars and the fifth wheel stand structure and this results in excessive impacts in the area of the fifth wheel plate, particularly in the king-pin receptacle which secures the trailer on the car. This causes excessive wear in this king-pin socket and as a consequence the fit of the pin in the socket becomes loose and may have the dangerous effect of allowing a trailer secured by such a worn connection, to become loosened, or detached from the hitch and possibly fall off the flat car.
These worn hitch connections have necessitated repairs to the top plate in the king-pin receiving area in order to restore some semblance of a safe connection for a trailer and the system of repairing these top plates in past general practice has consisted of directly building up the worn areas around a king-pin slot by weld metal applied to such areas, using flux cored welding wires in a multi-pass welding procedure until the build-up of the worn areas has been restored sufficiently to enable the king-pin opening to be machined to the normally specified size. This type of repair procedure has taken as little as one man hour, or as much as a full day, dependent upon the severity and the amount of wear encountered. This repair time is required for each hitch and in addition, the procedure entailed excessive material handling time as a result of both the welding and the machining operations.
The excessive wear conditions encountered in king-pin locking plates as a result of abrasion caused primarily by impacts has indicated a need for a consistently reliable repair procedure which afforded an economical means of restoring the top plate for quick return to normal service. A large number of hitches for both trailer and container service have been built and none of these hitches are immune to the severe wear that results from the service conditions normally encountered and therefore the need for a complete repair system has fully indicated the need for a reliable repair system to fill a gap that exists in the hitch repair field.
It has been known in the prior art to compensate for wear by the provision of a shim, or the like. Liners have been provided for this purpose and some of these have been installed after machining of a surface intended to mount the liner, but none of these has been integrated with the worn area and none has been provided for a fifth wheel plate. Examples of such prior arrangements are revealed in Pat. Nos. 3,473,854, 3,599,574, 3,711,927, 3,832,954 and 3,894,676.